1. Technical Field
The present disclosure relates to a lighting apparatus, and more particularly, to a lighting apparatus using an LED as a light source.
2. Related Art
In order to reduce energy, a lighting apparatus is designed to use a light source having high light emission efficiency based on a small amount of energy. Representative examples of a light source used in the lighting apparatus may include a light emitting diode (LED). The LED is differentiated from other light sources in terms of various aspects such as energy consumption, lifetime, and light quality.
Since the LED is driven by a current, a lighting apparatus using the LED as a light source requires a large number of additional circuits for current driving. In order to solve the above-described problem, an AC direct-type lighting apparatus has been developed to provide an AC voltage to the LED.
The AC direct-type lighting apparatus is configured to convert an AC voltage into a rectified voltage, and control the LED to emit light through current driving using the rectified voltage. Since the AC direct-type lighting apparatus directly uses a rectified voltage without using an inductor and capacitor, the AC direct-type lighting apparatus has a satisfactory power factor. The rectified voltage indicates a voltage obtained by full-wave rectifying an AC voltage.
The AC direct-type lighting apparatus includes one or more LED groups, and each of the LED groups includes one or more LEDs. Furthermore, the AC-direct type lighting apparatus may include a dimmer for dimming.
The lighting apparatus may turn on or off the LED groups in response to a change of a rectified voltage, and the luminance of the lighting apparatus may be controlled by dimming.
Typically, the lighting apparatus includes a plurality of LED groups connected in series. According to the change of the rectified voltage, a part of the LED groups may be turned on, and the other part of the LED groups may be turned off. Thus, an optical deviation corresponding to the change of the rectified voltage may occur. When light emission is performed in response to a rectified voltage controlled at a full angle, a significant optical deviation may occur.
Furthermore, the dimmer has a non-uniform operation characteristic. That is, when the phase angle of the rectified voltage is controlled through the dimmer, it is difficult to precisely control luminance. Then, a dimming deviation may occur, and an optical deviation may occur according to the dimming deviation.
The AC direct-type lighting apparatus needs to solve the problem in which an optical deviation occurs, in order to provide high-quality lighting.